Linear Regression

Reverse Polish Notation Calculators

Reverse Polish Notation (RPN) is an efficient, stack-based method for
operating an electronic calculator. Most Hewlett-Packard calculators
(e.g. HP-35s
and HP-50g)
use RPN, as do a few programming languages like
Forth.
With a little practice, you'll find that RPN is much easier, faster,
and less error-prone than the algebraic logic that comes built in to most calculators.

Besides buying a Hewlett-Packard calculator, here are some other options if you'd like to try RPN: